(Read caption)
A shopper leaves a Costco store in Portland, Ore.Hamm argues that buying in bulk may make groceries cheaper in some cases, but it may lead to using them more liberally, wiping away those savings.

First of all, if I have a lot of orange juice, I drink it faster. If I go to the store and buy one of the really large containers of orange juice, our family will go through the whole thing in three or four days. On the other hand, if I go to the store and buy a small container of orange juice, our family will go through the whole thing in… three or four days.

Why is that? Well, when we have an abundance of something, there’s a tendency to overconsume. I’ll drink it with breakfast, in the morning, in the afternoon… if I feel there’s a lot of orange juice left, I’ll drink it.

Second, although the cost per ounce of the big container of juice is lower than the smaller container, the big container does cost more. The sticker price on the 96 ounce container is substantially higher than the one on the 32 ounce container.

Now, you could easily argue that these points are moot because I’m talking about something non-essential to begin with. We don’t need orange juice, so the entire purchase is non-essential.

However, the same phenomenon exists with more essential purchases, too. Take hygiene products, for example.

Let’s say I buy a very large jug of shampoo at the store. I’m standing in the shower with it and I give it a little squeeze. Immediately, an overabundance of shampoo hits my hand. I don’t need that much shampoo. The thing is, even if I’m really careful, the nature of that large bottle often puts too much shampoo on my hand. It just goes to waste.

(On the other hand, when there’s just a little shampoo left, I tend to be very frugal and careful with it. I’ll use as little as possible so I can make the bottle last longer.)

Another example: spices. It might be less expensive per ounce to buy a large amount of dried thyme at a spice store, but if you can’t use it quickly and it sits in your pantry for a couple of years, it becomes useless, losing its flavor.

This leads us, again, back to bulk buying. Bulk buying doesn’t save you anything if you waste the excess. On top of that, having a large quantity of something often encourages wasteful use, like drinking too much orange juice or using too much shampoo or leaving too much thyme in your pantry.

Because of this, I’ve started to hold off on bulk buying unless it’s something that I’m not going to overconsume and I’m not going to waste. I buy small amounts of spices and I buy the small container of orange juice. With shampoo, I keep a small container in the shower and fill it occasionally from a big container I keep in the closet, which still causes me to have that “I only have a bit left … better make it last” attitude when in the shower.

What do I actually buy in bulk and use normally, though? Garbage bags. Household cleaning supplies. Liquid soap, particularly if I have a dispenser for it that allows me to dispense a squirt at a time. Individually packaged goods. Rechargeable batteries. In other words, non-perishables that I can’t easily overuse.

Bulk buying is a great idea, but if it leads to overconsumption or to waste, you’re not really gaining anything. Bulk buying only really shines when you’re buying something that you’ll use completely but not use excessively.